about simulating unaxial tension (MINGCHAO WANG)

Message: 1
Date: Tue, 17 May 2011 11:05:34 +1000
From: MINGCHAO WANG <[email protected]>
Subject: [lammps-users] about simulating unaxial tension
To: "[email protected]"
<[email protected]>
<[email protected]>
Content-Type: text/plain; charset="iso-8859-1"

Hi all,

I want to simulation unaxial tension. In my model, I use periodic boundary for
all three directions.
boundary p p p

and, I use fix deform for adding strain increment, and fix npt to control the
pressure of other 2 directions.

fix 5 all deform 100 x erate 0.01 units box

fix 6 all npt temp 300 300 0.005 y 0 0 0.05 z 0 0 0.05

My question is:

1. Is it OK for simulating unaxial tension?

2. In another article, they use the same boundary condition, but they use NVT
with fix deform for tension.

3. Can you give me some advice for simulating poisson's ratio?

Best regards,

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You typically don't want to use NVT unless you have reasoning for it in a
uniaxial deformation. To get proper poisson ratio, I use an NPT controller
in the perpendicular directions with the pressure set at 0.0 bar. I have
done it with 1.0 bar, but the literature seems to prefer using 0.0.
Unfortunately, I do not know the poisson ratio of my materials, so I can't
say whether or not it it accurate.

Kevin Hadley